Power over Ethernet (PoE) is an inline power technology that uses an Ethernet networking cable to deliver power to network devices that have Ethernet connectivity. In PoE technology, a device may be a powered device (PD) or an inline power source, sometimes referred to as power sourcing equipment (PSE). An inline power source is a device, such as an Ethernet switch, that provides or sources power to other devices through an Ethernet cable. A PD is a network device, such as a wireless access point, internet phone, etc., that is powered by the inline power source through an Ethernet cable.
In certain circumstances, a PD may be a network device that draws power from an inline power source, but that also provides power to one or more additional downlink PDs. Such network devices that both draw and source power are sometimes referred to as PD-PSE devices.